(190bs) Addressing Complexity of Health Impact Assessment in Industrially Contaminated Sites Via the Exposome Paradigm

Authors: 
Sarigiannis, D., Aristotle University of Thessaloniki
Karakitsios, S., Aristotle University of Thessaloniki
Health impact assessment in industrially contaminated sites is a complex process that entails consideration of various technical, environmental, societal and health-related aspects coupled to the associated uncertainties. The key questions in this regard can be summarised as follows:

(a) What type of compounds do we have to deal with? Typically, emissions vary significantly as a function of the industrially contaminated site activity type. Their intensity varies with the duration of activities, the environmental restoration measures applied and the amount of processed materials.

(b) How are these compounds distributed in the environment? Of particular interest in this regard are the environmental compartments in which chemicals are released and the physicochemical properties of the released compounds.

(c) What are the exposure levels to these compounds for the workers and the local population? Addressing this point requires assessing the contribution of multiple pathways and routes of exposure to the overall exposure burden, as well as reckoning the relative contribution of the industrially contaminated site sources to the exposure background in the vicinity.

(d) How does exposure to industrially contaminated sites related to adverse health outcomes? Answering the above requires integrated consideration of both epidemiological and toxicological evidence relating exposure to effects. This, however, needs to be sustained by the elucidation of the biological mechanisms underlying the exposure-to-effect continuum, i.e. the relevant adverse outcome pathway(s) linking the molecular biology of human disease onset and/or exacerbation and environmental co-exposure to the traditionally complex mixture of toxicants found in industrially contaminated sites.

In this work we present a novel approach to health risk and impact assessment of industrially contaminated sites that explores the connectivity among the different information layers pertinent to environmental characterisation on the one hand and the different scales of biological organisation in human beings (from gene regulatory networks to cell/tissue function allostasis to organism physiological perturbations).

Exposome aims at capturing the mechanistic processes that describe the sources to dose continuum. Towards this aim, several methodological tools are employed related to environmental and human biomonitoring. Starting from environmental exposure, various sensors including in situ systems for regulatory monitoring of environmental media, personal, wearable and remote sensors are combined for determining the external exposome, feeding fusion algorithms for integrating functionally these datasets and filling adequately data gaps in space and time.

External exposures are translated into internal dose both at systemic level and at target tissues using physiology-based biokinetic models that consider the different routes of exposure and the chemical and biochemical interactions among the pollutant mixture components. Biological perturbations at different are captured with multiple –omics (including genomics, transcriptomics, proteomics and metabolomics) and post-omics technologies including epigenomics.

Identification of the perturbations results in the identification of putative pathways of toxicity, that are verified by targeted multi-omics and functional assays. Advanced bioinformatics such as support vector machines and clustering algorithms and systems biology models allow us to identify the functional links among the data derived from high throughput testing platforms and disease phenotypes providing thus phenotypic anchoring of the mechanistic hypotheses made earlier. Finally, translation of individual into community effects is carried out using advanced statistic tools that allow the understanding of the connection among the investigated parameters, such as the environment-wide association studies (EWAS). Environmental factors that are correlated are not considered confounders; rather they are co-variates, which are in “linkage disequilibrium” with each other. EWAS is a population-based data analysis approach that correlates multiple environmental factors to disease. The EWAS approach is based on Genome-Wide Association Study (GWAS). In EWAS, the place of the genome domain is replaced by the envirome domain. The envirome consists of the environmental factors which are the quantity of the individual exposures that has directly measured. Particularly, the measures can be the amount of a chemical substances in human tissues and organs, a self-report historical exposure and common well–being characteristics such as family and social economic status (SES).

The methodology proposed above, has been applied in a characteristic type of ICS, the Fili landfill of Athens, the capital of Greece, which is populated with around 5 million inhabitants.The HERACLES (Waste Management) Greek cohort, is a study aiming at assessing the contribution of environmental contamination due to waste management practices in the urban and periurban environment associated to children neurodevelopment. The study has been established in 2012. Around 350 children aged 3 to 8 living in the proximity between 0.5 to 12 km were enrolled. For the association, several exposure factors have been investigated, including:

- Exposure to heavy metals, such as Cd, Hg and As in urine, Pb in blood, Mn and Hg in hair

- Additional proxies of exposure, such as distance from the contaminated sites, concentration of heavy metals in the soil of the child address

- Additional factors considered as exposure and effects modifiers such as:

o Sociodemographic parameters (socioeconomic status, mother education, father education, stress events)

o Child anthropometric parameters and post-delivery factors (child body mass index, child gender, breastfeeding, presence of micronutrients, minerals and vitamins, Se in the mother plasma during pregnancy, delivery and in cord blood)

o Detailed dietary habits, such as consumption of meat products (pork meat, beef, lamb, sausages), fish, sea food, poultry (eggs, chicken), dairy products (milk, yogurt), nuts, fruits, vegetables and snacks (biscuits, chocolates)

- Analysis of metabolomics profile from urinary samples and pathway analysis, for identifying the pathways that are perturbed and associated with the respective neurodevelopmental progress.

- Neurodevelopmental progress in children was estimated with the Wechsler Intelligence Scale for children – Fourth Edition, which is an individually administered measure of intelligence intended for children. WISC-IV yields measure of general intelligence as reflected in both verbal and nonverbal (performance) abilities and specific indices including verbal comprehension, perceptual reasoning, working memory and processing speed.

EWAS analysis showed that distance of the residence address from the waste management site is a key factor associated with almost all the indices of the WISC IV test. More specifically this variable shows a robust statistical association (p-value <0.001) with the Intelligence Quotient (IQ), Verbal Comprehension index, Perceptual Reasoning index, Working Memory index. Analysis of the results shows a positive association with the WISC IV scores indicating that living far from the waste management site has a positive impact on the children cognitive functions.Interesting conclusions can be drawn from the analysis of food consumption patterns. Tomato consumption appears to be statistically (p-value <0.05) associated with QI, Verbal Comprehension index and Working Memory index while cereal consumption reveals a strong association (p-value < 0.01) with the Perceptual Reasoning index. Both food items are positively associated with cognition indices meaning that their consumption has potential positive effects on the cognitive functions of the children. Epidemiological evidence suggests that consumption of lycopene, a natural antioxidant present in tomatoes, is able to reduce the risk of chronic diseases such as cancer, cardiovascular diseases as well as psychiatric syndromes. Consumption of fish showed a hybrid behavior depending on the type of fish and the neurodevelopmental indicator considered: higher consumption of white fish appears to have positive effects on the IQ and Verbal Comprehension index (p-value <0.001) while higher consumption of white fish reveals a negative effect (p-value <0.01) on Perceptual Reasoning index and Working Memory index. Among the sociodemographic parameters, it has been illustrated that mother and father educational level are positively associated with IQ and they comprise the second and third most significant parameters. Based on the metabolomics analysis and the subsequent bioinformatics analysis, several metabolic pathways were identifyied. With regard to the perturbed metabolic pathways, several pieces of indirect evidence exist that autophagy may degrade the glycogen in neurons, in a way similar to many other tissues. For example, defects in lysosomal enzyme acid alpha-glucosidase have been associated to glycogen accumulation in many tissues, including neurons; the concentration of glycogen in neurons provokes neurodegenaration. In practice, trehalose acts as a potent stabilizer of proteins able to preserve protein structural integrity and reduces aggregation of pathologically misfolded proteins. Trehalose is an mTOR-independent inducer of autophagy and, together with TSC, form a complex which is the key regulator of protein synthesis. Thus, they control cell growth. Recent data suggest that the TSC1/2 complex influences also neural polarity. The mevalonate cascade is a key metabolic pathway that regulates a variety of cellular functions and is thereby involved in the pathophysiology of many brain diseases, including neurodevelopmental and neurodegenerative disorders.

Exposome science can overhaul the current environmental health impact assessment paradigm, allowing us to effectively address the complexity related to the interplay of genetic, epigenetic, environmental, dietary and sociodemographic parameters. The application of the above methodology in a typical ICS (landfill), allowed us to conclude, that proximity to landfills and exposure to heavy metals, combined with sociodemographic and dietary parameters, results in metabolic pathways perturbation that are mechanistically associated with lower neurodevelopmental scores.